Yarn tension devices have long been used in conjunction with knitting and weaving machines to provide proper tension on the yarn as the yarn is fed to the machine. The prior workers in the art have developed various types of ball type and other yarn tensioning devices for this purpose. The ball type tensioning devices usually include a vertical passageway or channel within which are positioned a plurality of balls for tensioning purposes. The vertical passageway or channel usually terminates downwardly in a ceramic insert upon which the lowermost of the balls within the channel seats for yarn tensioning purposes as the yarn is fed through the tensioning device channel. The interaction of the balls and the seat results in tensioning the yarn by squeezing the yarn against the seat as the yarn is fed through the tensioning device. McCullough, U.S. Pat. No. 4,123,014 and Levin, U.S. Pat. No. 4,030,684 are examples of prior art ball tensioning devices wherein the yarn is fed vertically. McBride, Jr., U.S. Pat. No. 4,094,477 illustrates a vertical type ball tension device wherein the yarn is tensioned as it feeds horizontally through the device.
As disclosed in the above cited patents, the prior art yarn tensioning devices generally include a housing which defines a cylindrically shaped, vertically oriented yarn passageway. The yarn passageway is downwardly defined at the lower end thereof by a ceramic yarn eye insert which provides a seat for the lowermost ball within the passageway so that the ball normally remains seated upon the insert. In the design of the horizontal yarn device, a pair of diametrically opposed bottom inserts are provided and the lowermost ball seats upon the inserts.
In the case of ball tension devices designed for use with vertical yarns, it is usual to employ a threading device, such as a latchless knitting needle for yarn threading purposes. The latchless needle can be inserted downwardly through the yarn passageway and through the yarn opening defined in the bottom ceramic insert by displacing the balls laterally as necessary to pull the yarn through the device. Threading of the prior art ball tension devices has usually presented problems because of the physical size of the balls and the restricted diameter of the ball chamber. The respective dimensions have usually rendered it impossible to thread the device in a single pass with a straight threading instrument. It was often necessary to remove the cap and sometimes the balls in order to thread the device. This was cumbersome and often resulted in caps and balls being dropped onto the floor. In most prior art designs, the vertical alignment of the top ceramic insert in the tension device cap and the bottom ceramic seat and the position and size of the intervening steel balls have prevented threading the device in a single pass.
Once the yarn has been properly threaded through the yarn tension device for feeding to a weaving, knitting or other known type of yarn employing machine, the lowermost ball will then automatically return to its seat with the yarn being fed between the ball and the seat for yarn tensioning in the designed manner. In the case of heavy yarns, for example yarns suitable for use with carpets, it is presently the practice to provide ball tension devices of similar configuration but of increased dimensions and with larger and heavier balls. The use of such heavy balls renders these presently available larger yarn tension devices relatively more difficult to thread.